Synlogic, Inc. filed a Form 425 on November 5, 2026, communicating a press release from Caldera Therapeutics, Inc. reporting new Phase 1a clinical data for CLD-423 and announcing a new pipeline license agreement, in connection with the pending merger between Synlogic and Caldera.

Key Highlights

  • Phase 1a trial enrollment: The CLD-423 trial enrolled 56 healthy subjects, with 42 receiving CLD-423 and 14 receiving placebo, across five single ascending dose cohorts and two multiple-dose cohorts.
  • Tolerability profile: As of the interim analysis cutoff, no dose-limiting toxicities were reported; most adverse events were mild (Grade 1) and deemed unrelated to treatment, according to the filing.
  • Pharmacokinetics: The estimated serum half-life of CLD-423 after IV administration exceeded 40 days, and mean estimated absolute SC bioavailability was approximately 89%, the filing stated.
  • TL1A suppression: CLD-423 suppressed free TL1A to below the lower limit of quantification within two hours across all evaluated dose levels and routes of administration, the filing disclosed.
  • New pipeline license: Caldera entered into an exclusive worldwide license agreement with Qyuns Therapeutics Co., Ltd. (HKEX 2509.HK) for a preclinical-stage bispecific antibody program targeting IL-17 and TL1A.
  • Planned Phase 2 trials: Caldera plans to initiate a Phase 2b ulcerative colitis trial and a Phase 2a Crohn's disease trial in 2027, with induction results from the UC trial expected by the end of 2028.
  • Concurrent private placement: Caldera disclosed commitments for a private placement expected to generate approximately $278 million in gross proceeds from healthcare institutional investors and mutual funds.

CLD-423 Clinical Data and Pipeline Expansion in Context of Caldera-Synlogic Combination

According to the filing, Synlogic, Inc. (OTC:SYBX) submitted this Form 425 in connection with a proposed all-stock merger between Synlogic and Caldera Therapeutics, Inc., governed by an Agreement and Plan of Merger dated July 28, 2026. Under the terms described, both companies would merge with subsidiaries of a newly formed holding company, Sonic Holdco, Inc. The combined company plans to operate under the name Caldera Therapeutics, Inc. and intends to apply to list on the NYSE American under the ticker symbol "CALD," according to the filing.

The communication published by Caldera on November 5, 2026, reported an interim analysis of its Phase 1a CLD-423 trial. The filing stated that dosing has been completed and follow-up is continuing, with the longest single ascending dose cohort followed out to 169 days and multiple-dose cohorts out to 85 days. On immunogenicity, the filing reported that confirmed treatment-emergent anti-drug antibodies were detected in 8 of 42 CLD-423-treated participants, with titers described as "borderline or low-to-moderate," and that no ADAs were observed when CLD-423 concentrations were within the projected therapeutically relevant range. One Grade 2 serious adverse event of stroke in the first cohort was assessed as unrelated to CLD-423, and one participant discontinued after a Grade 2 infusion-related reaction, the filing noted.

Regarding the planned Phase 2 program, the filing disclosed that Caldera intends to submit an Investigational New Drug application to the FDA in the fourth quarter of 2026 for the Phase 2b ulcerative colitis trial, with first patient dosing anticipated in early 2027. The Phase 2a Crohn's disease trial is planned as an open-label, single-arm study to be conducted in China, with initial data expected in late 2027. Additional details about the newly licensed IL-17 x TL1A bispecific program are described as planned for disclosure in 2027.

What Was Disclosed

Synlogic filed a Form 425 containing a Caldera Therapeutics press release disclosing Phase 1a interim data for CLD-423, a new exclusive pipeline license with Qyuns, plans for Phase 2 IBD trials in 2027, and an approximately $278 million private placement commitment in connection with the pending merger.